Printing cylinders as used in the printing industry typically are of relatively massive construction, and must be supported in a manner providing maximum stability and concentricity of the printing cylinder during a printing production run. It is not unusual for such cylinders to have a length of 90" or more, and for them to be of relatively large diameter, diameters of 30" or more being practical, and diameters of 12-15" being in common usage. Such cylinders commonly are formed from cold rolled steel or aluminum of a thickness of 0.375 to 0.5 inches, and thus are of considerable weight, this requiring that the cylinders be securely locked to a supporting mandrel and be held in concentricity therewith during driving of the cylinder by the mandrel.
Such cylinders usually are installed on their supporting mandrel by heating the cylinder and then shrink-fitting in onto the mandrel in the manner taught in U.S. Pat. No. 2,787,956, Kirby, et al. Such an operation is a tedious and costly one to perform and also carries with it the disadvantage that the cylinder must be reheated in order to permit its removal from the mandrel and the substitution of a replacement cylinder therefor, and that the replacement cylinder also must be heated to permit its shrink-fitting onto the mandrel.
Attempts have been made to eliminate this disadvantage by providing the mandrel with pneumatically inflatable members which are expanded into supporting and driving engagement with the inner periphery of the cylinder in the manner taught in U.S. Pat. No. 3,253,323, Saueressig. Such pneumatically inflatable members, are, however, unpredictable in their operation, and can result in the cylinder being supported or moving out of concentricity with the mandrel, with consequential bouncing or oscillation of the printing cylinder when under high speed operation. Also, loss of pneumatic pressure can result in the cylinder being released during a printing run, with consequential damage to the cylinder and the rotary printing press, and, considerable hazard to persons in the vicinity of the printing press. Such printing cylinders have considerable mass and thus are capable of storing very considerable kinetic energy when rotated at high angular velocities, such as occurs during operation of the printing press.
Hydraulically expansible heads have been proposed for locating printing cylinders on a mandrel. An example of such a hydraulically expansible head is disclosed in U.S. Pat. No. 4,381,709, Katz. This prior proposal eliminates the problem of heat-shrinking the cylinder onto the mandrel, and also eliminates the problems of bouncing and lack of concentricity of the printing cylinder inherent in pneumatically actuated mandrels, and also problems arising from a loss of pneumatic pressure. In this construction, a pair of journals are ridgedly interconnected by a central sleeve that has been pinned to the respective journals, the respective journals having thin-walled cylindrical expansion diaphragms that are expanded radially outwardly into engagement with the interior of the printing cylinder by hydraulic pumps contained within the journals.
While this prior proposed construction is admirable for its intended purpose, it cannot accommodate an immediate need for the support of a cylinder of different length or diameter than the previous one.